Gathering Blue, Chapters 7-9

The woman was hanging strands on the drying rope.

From the text:

"A wee cott it is!" he called. "And there's the crone outside in the garden, with her crookedy hands full of rainbow!"
Kira hurried along, rounded the curve, and understood what he meant. In front of the tiny hut, a bent and white-haired old woman was working near a lush flower garden. She leaned toward a basket on the ground, lifted handfuls of bright-colored yarns — yellow of various shades, from the palest lemon to a deep tawny gold — and hung them across a rope that was strung from one tree to another. Deeper shades of rust and red were already hanging there.

The horrible smelling liquid (old piss) brings the color to life and sets it within the fabric.

Annabella replaced the lid, still laughing. "You save it and age it good," she said. "Then it brings the hue to life and sets it firm.